Selective drive mechanisms

ABSTRACT

An intermittent motion transmitting device wherein the output of a continually rotating shaft is transferred selectively through an epicyclic gear train to advance a driven member. In one instance, the epicyclic gear train has associated therewith an input shaft attached to a constant speed motor and an output shaft attached to a platen of a printer. A plurality of spaced cogs project from the output shaft and are singularly engaged by a first stop lever to insure precise line feed spacing and to prevent rotation of the platen while the printer is printing. Upon engaging a ratchet wheel controller with a second stop lever, the rotation of the input shaft is transmitted through the epicyclic gear train to the platen. When the second stop lever engages the ratchet wheel, the first stop lever disengages from a cog on the output shaft to release the platen for positive rotation by the motor through increments corresponding to one or more line feed operations.

[ 51 May 23, 1972 itz [54] SELECTIVE DRIVE MECHANISMS ma wa mm .m LG mm 99 av Raymond R. Seidlitz, Rolling .Meadows, Ill.

[72] Inventor:

Primary ExaminerAllan D. Herrmann [73] Assignee: Teletype Corporation, Skokie, lll. Attorney-J. L. Landis and R. P. Miller [22] Filed: Aug. 7, 1970 [21] Appl. No.: 61,882

[57] ABSTRACT An intermittent motion transmitting device wherein the output of a continually rotating shaft is transferred selectivel y through an epicyclic gear train to advance a driven member. In one instance, the epicyclic gear train has associated therewith an input shaft attached to a constant speed motor and an output shaft attached to a platen of a printer. A plurality of spaced cogs project from the output shaft and are singularly engaged by a first stop lever to insure precise line feed spacing and to prevent rotation of the platen while the printer is printing. Upon engaging a ratchet wheel controller with a second stop lever, the rotation of the input shaft is transmitted through the epicyclic gear train to the platen. When the second stop lever engages the ratchet wheel, the first stop lever disengages from a cog on the output shaft to release the platen for positive rotation by the motor through increments corresponding to one or more line feed operations.

6 Claims, 7 Drawing Figures v s v I a a a 2 3 l l l 2 2 PATENTEDMAYZBIBYZ 3,664,471

sum 1 UF 2 {T JZL/ a M 7 TUENE'H PATENTEDMAY 23 i972 SHEET 2 [IF 2 SELECTIVE DRIVE MECHANISMS- BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to new and improved selective drive mechanisms, particularly for transmitting rotary motion incrementally through an epicyclic train. A specific embodiment relates to new and improved selectively released line feed mechanisms that transmit rotar motion through epicyclic gear trains to drive a platen through predetermined numbers of incremental, recurrent distances corresponding to lines of print to be recorded on mediums.

2. Technical Considerations and Prior Art In operating certain high speed apparatuses in combination with signal utilization devices, e.g., tape readers, teletypewriters, electronic computers, etc., it is necessary to feed rapidly a sheet of paper being printed upon so that successive lines of print or coded indicia may be recorded or read rapidly. For example, any delay in feeding a sheet of paper will delay recording a successive line of print. Since many lines of print are usually recorded on a given sheet of paper, there can be a multiplicity of relatively short delays resulting in a relatively long total delav. This total delay is excessive when compared to the rapidity with which data is generated so that every reduction in this delay can result in considerable savings both in signal line time and device utilization time. Also, faster line feed can result in reducing or eliminating the need for format control," meaning special delays or mark-time signals that otherwise need to be employed to accomodate the inherentlv slow mechanical operating times.

Most paper line feeding mechanisms use a feed pawl in combination with a ratchet for turning a platen to feed a sheet of paper. These mechanisms are inherently slow in operation since the input drive for the feed pawl is initially at rest and must be put into motion before a paper or other feed can be effected.

When it is desired to skip one or more lines of print by feeding more than a single line of paper, the feed pawl and ratchet combination must repeat its operation a plurality of times, necessarily multiplying the number of individual delays and increasing the total delay. Often it is desired to form-feed a sheet of paper into the printer where a large space may, for example, be left at the bottom of a page or at the top of a page. In this situation considerable time may be expended in line feeding the sheet of paper if the feed pawl and ratchet combination has ,to repeat its operation a plurality of times in order to create the desiring spacing.

Summary of the Invention An object of this invention is to provide new and improved selective drive mechanisms, for transmitting rotary motion incrementally through an epicyclic train to drive a member through one or more increments.

The invention contemplates using an epicyclic train for transfering selectively the kinetic energy from a continuously rotating input shaft to move incrementally a driven member, such as in one example a platen of a printer. When it is desired to transfer energv through the epicyclic train, one element of the train is restrained from motion causing another element in the train to positively move the driven member.

The invention further contemplates arresting rotation of the driven member only at an integral multiple of incremental arcs so that the driven member will always be properly spaced.

Brief Description of the Drawings FIG. 1 is a perspective view of a line feed mechanism, in which a motor driven epicyclic-gear train incrementally rotates a platen used to feed a sheet of paper in a printer in accordance with one specific embodiment of the invention;

FIG. 2 is a top view of a portion of the mechanism shown in FIG. 1 at a different time, partially in section and showing the epicyclic gear-train arrangement;

FIG. 3 is a sectional view, partially cut away and taken along line 3-3 of FIG. 2, showing a first pivoted stop lever preventing rotation of the platen while a second pivoted stop lever allows rotation of an input-control gear in the epicyclic geartrain;

FIG. 4 is a sectional view similar to FIG. 3, but showing the first stop lever allowing the platen to rotate while the second stop lever is preventing rotation of the input control gear in the epicyclic gear train;

FIG. 5 is a top view partially in section of an epicyclic gear train illustrating an alternative embodiment of the invention;

FIG. 6 is a sectional view taken along lines 6-6 of FIG. 5, illustrating the operation of a stop lever used with the embodiment of FIG. 5; and

FIG. 7 is a sectional view taken along lines 7-7 of FIG. 5, illustrating the planetary arrangement of the epicyclic gear train disclosed in the embodiment of FIG. 5.

Detailed Description First Embodiment Referring now to FIG. 1, there is illustrated one specific embodiment of and use for the invention, in which a sheet of paper 10 is intermittently advanced by a driven platen 11. In order to engage the sheet of paper 10 positively, a generally conventional sprocket or feed wheel 12 with radial pins 13 meshes with uniformly spaced holes 14 along the edge of the paper, or a friction drive of known construction can be used to advance the paper. The platen 11 serves as a surface upon which to support the sheet of paper 10 at a recording or printing position. It is to be understood that recording may be effected by punches or magnetic heads and the printing may be effected by type pallets or an electrically controlled jet of ink.

A shaft 16 is attached rigidly to the platen I1, and as escape or cog wheel 17 is attached rigidly to the shaft. The cog wheel 17 has a plurality of circumferentially spaced cogs 18 which are adapted to be singularly engaged by a first stop lever 19 to prevent rotation of the platen 11 while the printer is printing. Each cog 18 is separated from its adjacent cog by an arcuate distance n (FIG. 3) which is a linear function of the desired space between the lines of print on the paper 10.

When the first stop lever 19 is released from engagement with an engaged cog 18, the platen l I will be rotated by a continuously rotating input shaft 21 which is linked to the platen selectively by an epicyclic gear train, designated generally by the numeral 22. A continuously rotating motor 23 drives the I shaft 21 continuously at a constant speed in a counterclockwise direction, as viewed in FIG. 1. When the shaft 21 is selectively linked or clutched by the epicyclic gear train 22 to the platen 11, the motor 23 is able to deliver its rotational kinetic energy to the platen extremely rapidly; for example, in the FIG. 1 embodiment, in approximately one millisecond.

As long as the first stop lever 19 is withheld from engagement with the cogs l8, platen 11 will continue to rotate and advance the paper 10. Depending on how long the stop lever 19 is withheld from the cog wheel 17, the paper 10 may be fed so as to be single spaced, double spaced or form fed. When the paper 10 has been advanced the desired number of spaces the stop lever 19 is reengaged with cog wheel 17. However, the cog wheel 17 will continue to rotate by its own momentum until the first stop lever 19 encounters one of the cogs l8, whereupon the cog wheel will cease rotation. A simple oneway clutch (not shown) may be used between the cog wheel 17 and the platen 11 to prevent rebound when the cog l8 strikes the lever 19. Since the increments n on the cog wheel 17 correspond to single line feed spaces on the paper 10, the advance of the paper 10 will always be interrupted at an integral multiple of the spaces on the paper thereby necessarily spacing the lines being printed on the paper properly.

Referring now to FIG. 2, the epicyclic gear train 22 may he basically composed of a bevelled reaction gear 26, a bevelled output reaction gear 27, and one or more bevelled drive pinions 28 (only one shown). The gear 26 is mounted for free rotation about the shaft 21 by a set of roller bearings 29, and is held in meshed engagement with the pinion 28 by a pair of collars 31 positioned on the shaft 21. The output gear 27 is meshed with the drive pinion 28 and is connected rigidly to the cog wheel 17 which in turn is connected rigidly to the shaft 16 and the platen 11. An arm 32 is connected to the shaft 21 perpendicularly thereto, and is rotated continuously in a counterclockwise direction by the shaft 21. The drive pinion 28 is mounted rotatably on the carrier shaft 32 and orbits about the axis of the shaft 21.

If the gear 26 is prevented from rotating and the output gear 27 is not, then the orbiting drive pinion 28 will roll on the gear 26 and will necessarily drive the output gear 27. On the other hand, if the output gear 27 is prevented from rotating and the gear 26 is not, then the orbiting drive pinion 28 will roll on the output gear 27 and will necessarily drive the gear 26. The epicyclic gear train 22 therefore acts as a motion transferring device or a clutch when either the gear 26 or the output gear 27 are alternately prevented from rotating.

Referring to FIGS. 1 and 3, and 4, the selective clutching action is accomplished by a 'rockshaft 33 on which are mounted rigidly the first stop lever 19 and a second stop lever 35. The first stop lever 19 has a stop lug 36 thereon which is adapted to be rotated into abutting engagement with one of the cogs 18 on the cog wheel 17 to arrest and prevent rotation of the platen l I. The second stop lever 35 has a series of closely spaced teeth 37 thereon for engaging another series of closely spaced teeth 38 on a ratchet wheel 39 which is secured through a cylindrical spacer 40 to the gear 26. The ratchet wheel is used as a brake and it is to be understood that other types of brake can be utilized to interrupt the rotation of the reaction gear 26.

Referring now to FIGS. 3 and 4, it can be seen that the first and second stop levers 19 and are secured and oriented on the rockshaft 33 so that only one of the stop levers can ever be in stopping position at a time. As seen in FIG. 3, when the rockshaft 33 is rotated clockwise so as to engage the lug 36 with one of the cogs 18, the stop lever 35 will be rotated so as to position the teeth 37 out of engagement with the teeth 38 on the ratchet wheel 39. As seen in FIG. 4, when the rockshaft 33 is rotated counterclockwise, the stop lug 36 is moved out of engagement with the cog 18 and the teeth 37 on the stop lever 35 are rotated into engagement with the teeth 38 on the ratchet wheel 39. By orienting the stop levers l9 and 35 so that only one is in the stopping position at a time, either the output gear 27 and the platen l 1 will be prevented from rotating while gear 26 is free to rotate; or the gear 26 will be prevented from rotating, while output gear 27 is free to rotate.

Referring now to FIGS. 1,2 and 3, when the rockshaft 33 is rotated in the clockwise direction the stop lever 19 moves the lug 36 into engagement with one of the cogs 18 on the cog wheel 17 preventing the output gear 27 from rotating. The shaft 21 which is rotating counterclockwise continuously orbits the carrier shaft 32 counterclockwise about the axis of the shaft 21 causing the teeth of the drive pinion 28 to react against the stationary teeth of the output gear 27 so that the drive pinion 28 rolls upon the output gear 27 and rotates counterclockwise about the axis of the carrier shaft 32. Since the teeth of the drive pinion 28 are also meshed with the teeth of the gear 26, the gear 26 will be rotatably driven about the shaft 21 in a counterclockwise direction by the drive pinion 28. The gear 26 is free to rotate because the stop lever 35 is not engaged with the ratchet wheel 39 at this time.

Referring now to FIGS. 1, 2 and 4, when the rockshaft 33 is rotated in the counterclockwise direction, the stop lever 19 disengages the lug 36 from the cog 18 on the cog wheel 17 and the output gear 27 is released for rotation. Immediately after releasing the output gear 27 for rotation, the teeth 38 of ratchet wheel 39 are engaged by the teeth 37 on the stop lever 35 thereby stopping the ratchet wheel and the gear 26 abruptly. This causes the teeth of the drive pinion 28 to immediately react against the now stationary teeth of the gear 26 and reverse the rotational direction of the drive pinion from counterclockwise rotation to clockwise rotation about the carrier shaft 32. As the drive pinion 28 rolls upon the stationary gear 26 it will drive the output gear 27 counter clockwise, thus causing the platen I 1 to rotate counterclockwise as previously described. The relative speeds are determined by the gear ratios selected, a 2.1 speed increase being provided in the example of FIG. 1 600 rpm for the output shaft 16 and platen).

When it is desired to stop rotation of the platen 11 so that a new line may be printed on the paper 10, the rockshafi 33 is again rotated in the clockwise direction to the FIG. 3 position. Just prior to positioning the lug 36 on the stop lever 19 in abutting relationship with one of the cogs 18 on the cog wheel 17 the teeth 37 on the stop lever 35 disengage from the teeth 38 on the ratchet wheel 39 releasing the gear 26 for rotation. When the stop lug 36 engages one of the cogs 18 on the cog wheel 17, the platen 11 and the output gear 27 immediately stop rotation causing the teeth of the drive pinion 28 to react against the stationary teeth of the output gear 27 thereby reversing rotation of the drive pinion 28 from clockwise rotation to counterclockwise rotation. The drive pinion 28 thereupon drives the gear 26 to rotate in a counterclockwise direction through a conventional one-way clutch (not shown). As illustrated in FIGS. 3 and 4, the width of the stop lug 36 on the stop lever 19 is less than the arcuate distance n while the distance between the teeth 37 is equal to an arcuate distance x between the teeth 38 of the ratchet wheel 39. The ratchet wheel 39 will stop almost immediately when the teeth 37 and 38 engage, whereas the cog wheel 17 will continue to rotate by its own momentum until the stop lug 36 engages one of the cogs 18. This feature insures that the platen 11 will always be positioned after an advance on n radius to properly space the lines of print on the paper 10 since the distance n is a function of the distance between the lines of print on the paper. Furthermore, this arrangement insures that the rotation of the platen 11 will be arrested at integral multiples of the distance n when it is desired to line feed the paper 10 more than one space, as when, for example, it is desired to double space or form feed the paper. Operation of First Embodiment Referring now to FIG. 1, in order to selectively control oscillatory motion of the rackshaft 33, operating devices such as first and second solenoids 43 and 44, respectively, are provided to subtend and move an armature 46 connected rigidly to the rockshaft 33. While the printing on the paper 10 is taking place, the first solenoid 43 is energized to keep the stop lever 19 in a clockwise position so as to engage the stop lug 36 with one of the cogs 18 on the cog wheel 17 and to disengage the teeth 37 from the teeth 38 on ratchet wheel 39. When it is desired to advance the paper 10, the first solenoid 43 is deenergized and the second solenoid 44 is energized causing the armature 46 to rotate in a counterclockwise direction to release the stop lug 36 from engagement with one of the teeth 18 while rotating the stop lever 35 toward the ratchet wheel 39 thereby causing the teeth 37 to engage the teeth 38 of the ratchet wheel. This allows the motor 21 to deliver torque to the platen 11 through the epicvclic gear train 22 as previously 17 explained.

In order to coordinate operation of the solenoids 43 and 44, a schematically illustrated line feed selector circuit 47 responds to the receipt of line feed signals to control the energization of the solenoids. When it is desired to single space the paper 10 a line feed signal is received in the circuit 47 and functions to control the energization of the solenoid 44 and de-energize action of the solenoid 43 for a period of time sufficient to disengage the stop lug 36 from the cog 18. After the released cog 18 rotates past the stop lug 36, the solenoid 43 is again energized to bring the stop lug 36 back into position to engage the next succeeding cog 18 to stop rotation of platen 11. When it is desired to double space or form feed the paper 10 a line feed signal from the circuit 47 energizes the solenoid 44 and de-energizes the solenoid 43 for longer periods of time to allow additional cogs 18 to rotate past the withdrawn stop lug 36. Second Embodiment Referring now to FIGS. 57, there is shown a further embodiment of invention employing a different type of epicyclic gear train, designated generally by the numeral 50, in which planetary gears are utilized. In this embodiment, a shaft 51 is driven bv the motor 23 (FIG. 1). Attached to or formed on the end of the shaft 51 is a flanged carrier 52 with a three equally spaced carrier shafts 53 projecting therefrom. Rotatably mounted on each carrier shaft 53 is a planet gear 54. Each planet gear 54 is in turn meshed with the internal teeth 55 on a ring or reaction gear 56 secured to a sleeve 57 which is rotatably mounted within a bearing cage 58. Co-extensive with the shaft 51, but axially spaced therefrom is an output shaft 59 having a sun or reaction gear 60 rigidly secured to the end thereof adjacent the carrier 52. The sun gear 60 meshes with the planet gears 54 and functions to drive the output shaft 59 and the platen 11.

A cog wheel 61 with a plurality of cogs 62 spaced around the periphery thereof is ridigly attached to the shaft 59. The cogs 62 on the cog wheel 61 are adapted to be engaged by a stop lug 63 on a rockshaft 64 to prevent rotation of the platen 11 while the printer is printing on the paper 10. The selective release of the stop lug 63 initiates the transmission of motion to affectuate one or more line feed advances of the platen l 1.

A set of inwardly projecting ratchet teeth 66 are positioned internally around the interior of the ring gear 56. The ratchet teeth 66 on the ring gear 56 are engaged by a set of gear sector teeth 67 of a gear sector 70 secured to the rockshaft 64 to enable the transmission of torque through the planetary gear train 50 to rotate the platen 11 through one or more line feed operations.

As best seen in FIG. 6 the stop lug 63 projects toward the cog wheel 61 while the gear sector teeth 67 project toward the ratchet teeth 66 on the ring gear 56. When the rockshaft 64 is rotated in the counterclockwise direction the stop lug 63 engages one of the cogs 62 on the cog wheel 61 to prevent rotation of the platen l 1. However, when the rockshaft 64 is rotated in the clockwise direction the cog wheel 61 is released for rotation and the gear sector teeth 67 engage the ratchet teeth 66 on the ring gear 56 arresting rotation of the ring gear. In other words, the stop lug 63 and gear sector teeth 67 are positioned on the rockshaft 64 so that either the stop lug 63 is in blocking engagement while the gear sector teeth 67 are disengaged or the stop lug 63 is disengaged while the gear sector teeth 67 are in blocking engagement.

Operation of the Second Embodiment In operation of the embodiment shown in FIGS. 5, 6 and 7, the stop lug 63 is initially in engagement one of the cogs 62 on the cog wheel 61 to prevent the platen l 1 from rotating as the printer is printing on the paper 10. The ring gear 56 is free to rotate because the ratchet teeth 66 on the ring gear are not engaged by the teeth 67 of gear sector 70. Since the sun gear 60 is secured rigidly to the cog wheel 61 the sun gear is held stationary. As the shaft 51 rotates in the counterclockwise direction, and planet gears 54 orbit the sun gear 60, the teeth of planet gears 54 react against the stationary teeth of the sun gear 60 causing the planet gears to roll on the sun gear and rotate in a counterclockwise direction. Since the gear teeth on the ring gear 56 mesh with the teeth on the planet gears, the ring gear will be driven in a counterclockwise direction by the orbiting planet gears 54.

When it is desired to advance the paper one or more spaces, a line feed signal is applied to a line feed selector circuit, such as the circuit 47 schematically illustrated in FIG. 1, which functions to control the energization of the solenoids to rotate the rockshaft 64 in a clockwise direction. As the rockshaft 64 rotates clockwise, the stop lug 63 first releases the cog wheel 61 and then the teeth 67 of gear sector 70 are moved to mesh with the ratchet teeth 66 on the internal surface of the ring gear 56. Since the ring gear 56 is now held stationary the gear teeth on the planet gears 54 will react against the stationary gear teeth on the ring gear thereby reversing the rotational direction of the planet gears 54 and causing them to roll upon the ring gear while rotating about the carrier shafts 53 in a clockwise direction. Since the planet gears 54 are meshed with the sun gear 60 they will cause the now unrestrained sun gear to rotate in a counterclockwise direction thereby rotating the platen l 1 and line feeding the paper 10.

When the paper 10 has advanced the desired number of spaces, the energization of the solenoids is reversed to cause the rockshaft 64 to rotate counterclockwise into engagement with the cog wheel 61. Since the cogs 62 are uniformly spaced about the periphery of the cog wheel 61, the cog wheel will continue to rotate by its own momentum until the stop lug 63 engages one of the cogs thereby stopping the cog wheel, the sun gear 60 and platen 11 to properlv space the paper 10 at an integral number of line spaces. Just prior to moving the stop lug 63 into position to engage one of the cogs 62, the teeth 67 on the gear sector 70 disengage from the teeth 66 on the ring gear 56 freeing the ring gear for rotation by the planet gears 54. The ring gear 56 is rotated in the counterclockwise direction as soon as the teeth of the planet gears 54 react against the now stationary teeth of the sun gear causing the planet gears to drive the ring gear as they walk around the sun gear while rotating about the carrier shafts 53 in a counterclockwise direction.

It is to be understood that the described mechanisms are simply illustrative of two alternative embodiments of the invention and many modifications may be made in accordance with the disclosed principles of the invention.

I claim 1. In a mechanism for transmitting torque intermittently from a continuously rotating input shaft to an output shaft:

a sun gear rigidly attached to the output shaft for rotating the output shaft;

at least one planet gear driven by the input shaft and meshing with the sun gear for orbital motion around the sun gear;

a ring gear coaxially mounted with but spaced from said sun gear, said ring gear having inwardly projecting gear teeth meshing with the planet gear;

a plurality of circumferentially projecting first stops spaced about and on the output shaft;

a set of inwardly projecting second stops disposed adjacent to said gear teeth on said ring gear; and

motion control means selectively operated for disengaging a first stop and engaging a second stop to transmit rotary motion from the input shaft to rotate the output shaft and for engaging a first stop and disengaging a second stop to prevent rotation of the output shaft.

2. In a line feed apparatus for advancing a platen,

a first member having first stops circumferentially spaced thereabout at n radians apart corresponding to a single line space advance of the platen,

means for transferring motion from said first member to the platen,

a second member having second stops circumferentially spaced thereabout at x radians apart, where .r is less than a mechanism interposed between the first and second members for transmitting motion through the transferring means to the platen when a stop on the second member is engaged and no stops on the first member are engaged and for interrupting transmission of motion when one of the stops on the first member is engaged and the stop on the second member is disengaged,

drive means for continuously applying motion to said mechanism, and

means selectively operated for disengaging a first stop and engaging a second stop to apply motion from the drive means through said mechanism and transferring means to advance the platen and for disengaging the second stop and engaging a first stop to interrupt the advance of the platen after moving y times n radians where y is a positive integer.

3. In a mechanism for selectively rotating a platen a first gear for rotating the platen,

a shaft axially aligned with and spaced from said first gear,

a second gear meshing with said first gear, means mounting said second gear on said shaft for orbital motion about the axis of said shaft and for rotation on said first gear,

a third gear meshing with said second gear,

means for rotating said shaft, and

reversible means for selectively locking said first gear and releasing said third gear to roll said second gear on said first gear to drive said third gear and for locking said third gear and releasing said first gear to roll said second gear on said third gear to drive said first gear and rotate the platen.

4. The mechanism of claim 3 wherein said first, second and third gears are bevel gears.

5. The mechanism of claim 3 wherein said first gear is a sun gear, said second gear is a planetary gear and said third gear is a ring gear.

6. A mechanism for rotating a platen incrementally through selected integral multiples of an arcuate distance corresponding to selected integral multiples of a single line space advance of a strip of paper;

an input shaft;

means for continuously rotating said input shaft;

a carrier shaft attached to and projecting from said input shaft;

a drive pinion rotatably mounted on said carrier shaft;

a reaction gear rotatably mounted relative to said input shaft and meshed with said drive pinion;

an output shaft spaced from said input shaft;

means for transferring rotation from said output shaft to said platen;

an output gear positively secured to said output shaft and meshed with said drive pinion;

a cog wheel positively secured to said output gear and having a plurality of cogs spaced circumferentially therearound wherein each cog is spaced from adjacent cog by a distance corresponding to a single line space advance of the platen;

a first stop member for releasably engaging said cogs on said cog wheel to prevent rotation of said cog wheel and said platen;

a circular ratchet having teeth positioned circumferentiallv thereabout and spaced apart a distance less than the distance between said cogs on said cog wheel, said ratchet being secured rigidly to said reaction gear;

a second stop member for releasably engaging said teeth on said circular ratchet to prevent rotation of said ratchet and said reaction gear; and

means for selectively moving the second stop member into engagement with said ratchet teeth while moving the first stop member out of engagement with one of said cogs for rotating said output gear to rotate said platen, said moving means also moving the first stop member into position to be engaged by another advancing cog to interrupt rotation of the output gear, output shaft and platen at integer multiples of a single line space advance on a strip of paper. 

1. In a mechanism for transmitting torque intermittently from a continuously rotating input shaft to an output shaft: a sun gear rigidly attached to the output shaft for rotating the output shaft; at least one planet gear driven by the input shaft and meshing with the sun gear for orbital motion around the sun gear; a ring gear coaxially mounted with but spaced from said sun gear, said ring gear having inwardly projecting gear teeth meshing with the planet gear; a plurality of circumferentially projecting first stops spaced about and on the output shaft; a set of inwardly projecting second stops disposed adjacent to said gear teeth on said ring gear; and motion control means selectively operated for disengaging a first stop and engaging a second stop to transmit rotary motion from the input shaft to rotate the output shaft and for engaging a first stop and disengaging a second stop to prevent rotation of the output shaft.
 2. In a line feed apparatus for advancing a platen, a first member having first stops circumferentially spaced thereabout at n radians apart corresponding to a single line space advance of the platen, means for transferring motion from said first member to the platen, a second member having second stops circumferentially spaced thereabout at x radians apart, where x is less than n, a mechanism interposed between the first and second members for transmitting motion through the transferring means to the platen when a stop on the second member is engaged and no stops on the first member are engaged and for interrupting transmission of motion when one of the stops on the first member is engaged and the stop on the second member is disengaged, drive means for continuously applying motion to said mechanism, and means selectively operated for disengaging a first stop and engaging a second stop to apply motion from the drive means through said mechanism and transferring means to advance the platen and for disengaging the second stop and engaging a first stop to interrupt the advance of the platen after moving y times n radians where y is a positive integer.
 3. In a mechanism for selectively rotating a platen a first gear for rotating the platen, a shaft axially aligned with and spaced from said first gear, a second gear meshing with said first gear, means mounting said second gear on said shaft for orbital motion about the axis of said shaft and for rotation on said first gear, a third gear meshing with said second gear, means for rotating said shaft, and reversible means for selectively locking said first gear and releasing said third gear to roll said second gear on said first gear to drive said third gear and for locking said third gear and releasing said first gear to roll said second gear on said third gear to drive said first gear and rotate the platen.
 4. The mechanism of claim 3 wherein said first, second and third gears are bevel gears.
 5. The mechanism of claim 3 wherein said first gear is a sun gear, said second gear is a planetary gear and said third gear is a ring gear.
 6. A mechanism for rotating a platen incrementally through selected integral multiples of an arcuate distance corresponding to selected integral multiples of a single line space advance of a strip of paper; an input shaft; means for continuously rotating said input shaft; a carrier shaft attached to and projecting from said input shaft; a drive pinion rotatably mounted on said carrier shaft; a reaction gear rotatably mounted relative to said input shaft and meshed with said drive pinion; an output shaft spaced from said input shaft; means for transferring rotation from said output shaft to said platen; an output gear positively secured to said output shaft and meshed with said drive pinion; a cog wheel positively secured to said output gear and having a plurality of cogs spaced circumferentially therearound wherein each cog is spaced from adjacent cog by a distance corresponding to a single line space advance of the platen; a first stop member for releasably engaging said cogs on said cog wheel to prevent rotation of said cog wheel and said platen; a circular ratchet having teeth positioned circumferentially thereabout and spaced apart a distance less than the distance between said cogs on said cog wheel, said ratchet being secured rigidly to said reaction gear; a second stop member for releasably engaging said teeth on said circular ratchet to prevent rotation of said ratchet and said reaction gear; and means for selectively moving the second stop member into engagement with said ratchet teeth while moving the first stop member out of engagement with one of said cogs for rotating said output gear to rotate said platen, said moving means also moving the first stop member into position to be engaged by another advancing cog to interrupt rotation of the output gear, output shaft and platen at integer multiples of a single line space advance on a strip of paper. 